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CALIBRATION HANDBOOK

OF

MEASURING INSTRUMENTS

Alessandro Brunelli

Copyrighted Material


FIRST EDITION

NoticeThe information presented in this publication is for the general education of the reader. Because neither the author

nor the publisher has any control over the use of the information by the reader, both the author and the publisherdisclaim any and all liability of any kind arising out of such use. The reader is expected to exercise sound professionaljudgment in using any of the information presented in a particular application.

Additionally, neither the author nor the publisher has investigated or considered the effect of any patents on theability of the reader to use any of the information in a particular application. The reader is responsible for reviewing anypossible patents that may affect any particular use of the information presented.

Any references to commercial products in the work are cited as examples only. Neither the author nor thepublisher endorses any referenced commercial product. Any trademarks or tradenames referenced belong to therespective owner of the mark or name. Neither the author nor the publisher makes any representation regarding theavailability of any referenced commercial product at any time. The manufacturer’s instructions on the use of anycommercial product must be followed at all times, even if in conflict with the information in this publication.

Copyright © 2017 International Society of Automation (ISA)All rights reserved.

Printed in the United States of America. 10 9 8 7 6 5 4 3 2

ISBN: 978-1-945541-57-5

No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means,electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher.

ISA67 T. W. Alexander DriveP.O. Box 12277Research Triangle Park, NC 27709

Library of Congress Cataloging-in-Publication Data in process

Disclaimer: Neither the Author nor the Publisher are responsible for the results obtained by the use or possiblemisuse of the spreadsheets used in this handbook or on the CD.

The literary property and all rights of the series of ISA Publications are reserved to the Publisher. The graphicalstructure, the editorial content, and illustrations in this volume cannot be reported, translated, or stored, even partially,without the permission of the Publisher.



3

TABLE OF CONTENTS

Preface 5

Part I – Requirements and General Guidelines for Management of Instruments and Measurements 7

1. International System of Units (SI) 92. International Calibration System (ILAC) 153. European Calibration System (EA) 174. Traceability and Compatibility of the Measures 215. Measurement Uncertainty 236. Calibration of Measuring Instruments 297. Requirements in the Quality Management Systems ISO 9001, 14001, 16949, and EN 9100 358. Requirements in the Measurement Management Systems ISO 10012 399. Criteria for Instrument Selection in Relation to the Measurement Requirements 4910. Criteria for Conformity Evaluation of the Measuring Instrument 5311. Notes to Legislative Requirements for Initial and Periodic Calibration Checks 5912. Notes to Technical Requirements on Document Management According to FDA 21 CFR Part 11 65

Part II – Requirements and Criteria for the Management and Calibration of Measuring Instruments 71

1. Physical Quantities 731.1 Pressure 751.2 Flow 871.3 Level 1131.4 Temperature 1191.5 Humidity 1431.6 Viscosity 1531.7 Density 1631.8 Mass 175

2. Chemicals for Liquids 1912.1 pH 1932.2 Redox 1992.3 Turbidity 2052.4 Conductivity 2112.5 Dissolved Oxygen 2172.6 Dissolved Ions 2232.7 Colorimetry 2292.8 Refractometry 235

3. Chemicals for Gases 2413.1 Infrared Analyzers 2433.2 Ultraviolet Analyzers 2473.3 Comburent Gases 2513.4 Combustible Gases 2553.5 Chromatography 2613.6 Spectrometry 267

4. Mechanical Quantities 2734.1 Length 2754.2 Force 2874.3 Torque 2914.4 Velocity (and Rotation) 2954.5 Vibration (and Acceleration) 2994.6 Sound and Noise 305

5. Electrical Quantities 3155.1 Indicators 3175.2 Oscilloscopes 3215.3 Transformers 3255.4 Energy Meters 3295.5 Clamp Meters 3335.6 Multimeters 337

Analytical Index for Acronyms, Terms, and Instruments to be Calibrated 341



5

Dedication

To my learned readers, this book combines my so-called HME versus HMS,or How Much is Enough versus How Much it Serves,

in compliance with metrological requirementsimposed by the reference normatives for

calibrating and confirming measuring instruments.

In loving memory of my beloved wife, Romanella, who always encouraged me to give the best of myself.

PREFACE

The Calibration Handbook of Measuring Instruments was commissioned by the Association for the Instrumentation,Control and Automation Company in Italy (GISI) to meet the needs of instrumentation technicians, who stronglyrequested a handbook that clearly and completely explained calibration procedures and periodic metrologicalconfirmation for all the instruments for measurement in industrial applications: chemical, petrochemical,pharmaceutical, food, energy, and custody and transfer for water, oil, and gas.

Published first in the Italian language in 2012, it was outstandingly successful; many companies, professionals, andtraining centers have found this calibration handbook a valuable reference.

FOREWORD

The handbook is mainly dedicated to operators involved in the verification and calibration of measuring instrumentsused in ISO 9001 – Quality management systems, ISO 14001 – Environment applications, ISO 16949 – Automotiveindustry, and EN 9100 – Aviation industry to be a reference and consultation handbook in the main topics for theassurance and management of industrial process measurement, such as:

• The general concepts for managing the measurement equipment according to ISO 10012 concerning themanagement system of instruments and measurements

• The ability of the instrument to perform accurate measurements, by controlling the drift to maintain the qualityof the measurement process

• The criteria and procedures for acceptance, management, and verification of the calibration of the mainindustrial measuring instruments

• The provisions of law and regulations for production and the European marking, CE, of metrologicalinstruments used in commercial transactions and for their periodic verification

The handbook consists of two main parts:

• Part I illustrates the International System of Units (SI) and the international, European, and national calibrationservices (ILAC, EA, and others) and then the performance requirements of the instruments for measuring andthe criteria for assessing the traceability and uncertainty of the measurements. It also covers the technical andregulatory requirements relating to the management of instruments and measurements.

• Part II describes the problems of calibration, verification, and metrological confirmation for the main families ofinstruments for measuring physical, chemical, mechanical, and electrical quantities. Then, for each quantity, itdescribes the specific concepts of the measure and the main reference standards, and then presents the mostcommon types of instruments, simple calibration procedures, and metrological confirmation. This isaccompanied by the format for collecting and processing experimental data, suitable for recording and editingthe calibration report of metrological confirmation.



GENERAL GUIDELINES

6

For the most common measurement instruments, it is possible to determine the best practices for calibrationprocedures suitable for industrial applications, with procedures harmonized on the following points:

• Scope and purpose• Identification and classification• Normative references• Ambient conditions• Initial checks• Calibration method• Calibration verification• Calibration results• Metrological confirmation

Practical report templates useful for recording both the recorded instrument data and the experimental calibration data,to evaluate the conformity of the instrument, are available on the enclosed CD for practical usage.

The report templates are reported in “white” on the enclosed CD for a practice specific use.

Furthermore, the CD contains various spreadsheets in Excel (Reports Calibration) that automatically calculate errorsand the relative uncertainty of measurement. They directly determine the compliance of the calibrated instrumentaccording to the two methods mentioned in this calibration handbook: as a practical method, according to the errorapproach, or an analytical method, according to the uncertainty approach.

Therefore, once again, the author aims to develop and promote the culture of instrumentation in its metrological andapplication aspects, currently the cornerstone of a company’s production as traceability and compatibility ensuremeasurements in the global market.

ABOUT THE AUTHOR

Alessandro Brunelli has worked for more than 40 years in the field of training andcertification in industrial instrumentation at an experimental laboratory. He graduated fromthe Higher Institute of Industrial Technology Mechanical of the Polytechnic (University) ofMilan in 1974 and later became a professor of mechanical and thermal measurement atthe Polytechnic of Milan.

As a technologist, Brunelli participates in the activities of National, European, andInternational standardization for mechanical and electronic equipment. He is responsiblefor the Italian National Unification (UNI) commission on “Metrology of Pressure andTemperature” and is secretary of the technical committee Italian ElectrotechnicalCommittee (CEI) on “Industrial-Processes Measurement, Control and Automation.”

During his career, Brunelli published many papers in the areas of measurement andautomation of industrial processes. He published two monographs relating to humidity andflow measurement, a series of five volumes on measurement and control in industrial applications, a specific volumetitled Industrial Measurements: Physical & Mechanical, and a two-volume Instrumentation Handbook series.




7

PART I

Requirements and General Guidelines for Management of Instruments and Measurements

1. International System of Units (SI)

2. International Calibration System (ILAC)

3. European Calibration System (EA)

4. Traceability and Compatibility of the Measures

5. Measurement Uncertainty

6. Calibration of Measuring Instruments

7. Technical Requirements in Quality Management Systems ISO 9001, 14001, 16949, and EN 9100

8. Technical Requirements in Measurement Management Systems ISO 10012

9. Criteria for Instrument Selection in Relation to the Measurement Requirements

10. Criteria for Conformity Evaluation of the Measuring Instruments

11. Notes to Legislative Requirements on Initial and Periodic Calibration Checks

12. Notes to Technical Requirements on Document Management according to FDA 21 CFR Part 11



INTERNATIONAL SYSTEM OF UNITS (SI)

9

1 International System of Units (SI)1

1.1 Introduction

The International System of Units (in French: Système International d’unité), abbreviated SI, is the internationalreference system for expressing measurement results all over the world. The International System was established in1960 as a result of the Metre Convention of 1875, which sought to coordinate all metrological activities at all levels:

• Scientific and diplomatic• International and national

It did this through the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures[CGPM]), which was formed by the delegates of the member states to the Metre Convention and still has these tasks(see figure 1-1):

• Discuss and promote the necessary measures to spread and refine the SI system• Recognize the results of new fundamental metrological determinations• Issue scientific resolutions of international scope• Approve the definition of the SI units

The CGPM uses the work of the International Committee for Weights and Measures (Comité International des Poids etMesures [CIPM]), composed of members appointed by the same CGPM. Their task is to carry out the decisions of theCGPM and oversee the activities of the International Bureau of Weights and Measures (Bureau International des Poidset Mesures [BIPM]).

This latter institution is an international metrological laboratory based in Sèvres near Paris. It is the permanent scientificbody of the CGPM and has the following tasks:

• Preserve the international prototypes of measurement standards• Carry out and coordinate the determination of fundamental physical constants• Make the necessary comparisons to ensure the uniformity of international measures

The units, terminology, and International System recommendations are established by the General Conference ofWeights and Measures, the diplomatic body that is connected with the BIPM.

The International System of quantities and units has thus developed over time:

• 1889: the “MKS system” with only three units (meter, kilogram, second), approved by the first CGPM• 1935: the “MKSΩ system” with a fourth unit (ohm) dedicated to electrical resistance, on the proposal of the

Italian physicist Giovanni Giorgi• 1946: the “MKSA system” with a variation of the fourth unit: ampere electric current, based on the Giorgi

proposal and therefore also commonly called the “Giorgi system”• 1954: the “SI system” with the addition of kelvin and candela, approved by the 10th CGPM• 1971: the “SI system” included a seventh unit, the mole, approved by the 14th CGPM

Therefore, currently the International System:

• Is based on seven fundamental quantities (with the respective units of measurement) (see table 1-1)• Is made up of other so-called derived quantities (and their units) (see table 1-2 for the variables that have

proper names and table 1-3 for other units.)• Includes prefixes to identify the different sizes of the various units of measurement (see table 1-4)

1. The measurement units of the International System (SI) are currently regulated by the International Standards ISO/IEC 80000 series, replacing the previous standard ISO 31 and IEC 60027 series.



GENERAL GUIDELINES

10

The International System is therefore a coherent system in that its magnitudes and derived units are derived as aproduct of magnitudes and fundamental units.

Figure 1-1. International Organization of Metrology

Diplomatic Level

Technical Level

CGPM

METRE CONVENTION

CIPM BIPM

NATIONAL LABORATORY

ADVISORY COMMITTEES(quantities of competence)

1 – Electricity and Magnetism 2 – Photometry and Radiometry 3 – Thermometry 4 – Length 5 – Time and Frequency 6 – Ionizing Radiation 7 – Units of Measurement 8 – Mass and Related Quantities 9 – Quantities of Substance 10 – Acoustics, Ultrasound, and Vibration i i

CGPM = Conférence Génerale des Poids et Mesures (General Conference of Weights and Measures)

CIPM = Comité International des Poids et Mesures (International Committee of Weights and Measures)

BIPM = Bureau International des Poids et Mesures (International Bureau of Weights and Measures)



INTERNATIONAL SYSTEM OF UNITS (SI)

11

1.2 Writing Rules Used in the International System

To standardize the writing and avoid misinterpretation, the SI provides some rules for writing units of measurement andtheir symbols:

a) Units writingA unit of measure should be written:

• In full and without accents or diacritical marks if it is introduced in a discursive text (e.g., leakage current of afew milliamperes and not a few mA)

• With the symbol if included in a formulation with quantitative rather than qualitative value (e.g., 10 mA and not10 milliamperes)

b) Symbols writingUnits of measurement symbols are identified as follows:

• With a small letter, if the unit is derived from the name of a unit (e.g., m for meter, cd for candela)• With a capital letter, if the unit is derived from the name of a person (e.g., A for Ampere, V for Volta, W for Watt)

The only exception is for liter, where both the symbols l and L are acceptable.

c) Quantities writingRegarding quantities detected or identified by units of measure, SI symbols:

• Should never be followed by a period (e.g., write 10 mm and not 10 mm.)• Should be placed after the numeric value (e.g., write 10 mm and not mm 10)• Must be separated from the numeric value by a space (e.g., write 10 mm and not 10mm)• Can be derived quantities written without spaces or interposed by “.” or “/” (e.g., Nm or N.m, ms-2 or m/s2)

d) Numbers writingFinally, regarding separating the numbers of the quantity values:

• Use a space to separate them with the whole numbers in groups of three (no points or commas); for example,1 000 000 and not 1.000.000 or 1,000,000.

• Use a comma as the separator between the whole numbers and decimal ones, except for using the decimalpoint in English-language texts (CGPM of 2003).

The SI should be used in each country. In some of them, such as in Italy, their use is mandatory, in compliance with theEEC Council Directive 18 October 1971 (71/1354/ EEC), as amended on 27 July 1976 (76/770/EEC). Its use ismandatory in drafting acts and documents with legal value, and therefore the failure to comply with the above rules ofwriting could invalidate such documents.



CALIBRATION OF MEASURING INSTRUMENTS

29

6 Calibration of Measuring Instruments

6.1 Introduction

The control of measuring instruments, namely:

• Measuring equipment in the ISO 9001 – Quality management systems• Surveillance equipment in the ISO 14001 – Environmental management systems

ensures, where necessary for valid results, that the measuring instruments are:

• Calibrated and verified, at specified intervals or prior to use, against measurement standards traceable tointernational or national measurement standards. Where no such standards exist, they must be registered withthe criteria used for calibration or verification.

• Adjusted or regulated again, when necessary.

Therefore, all management systems provide the initial calibration and any periodic “adjustment or metrologicalconfirmation” (according to ISO 10012 – Measurement management systems) of the measuring instruments to validatethe various measurement processes to ensure proper traceability of measurements to the International System (SI) (forterminology, see table 6-1).

6.2 General Calibration Conditions

To correctly perform a calibration, one must have infrastructure, means, methods and procedures, and appropriatestaff, or possess the four fundamental pillars:

Ambient ConditionsIf the measurement ambient is industrial, it is appropriate that the measures are carried out within these maximumlimits:

• Temperature : 20 ± 5°C (or 25 ± 10°C)• Relative humidity : 50 ± 25%

This contains the thermal drift of the standard and calibration instruments.

If, however, the measurement is made in a laboratory, it is appropriate that the measures are carried out in controlledconditions, within these maximum limits:

• Temperature : 20 ± 2°C for mechanical measurements, 23 ± 3°C for electrical measurements• Relative humidity : 50 ± 10% (or ± 20%)

This gives better uncertainty, and therefore traceability, of the measuring process.

Measurement EquipmentUse appropriate equipment for the measuring ranges and the desired levels of uncertainty, traceable to the SI units(see point 1) by:

• National calibration laboratories (NCL):o European cooperation for Accreditation (EA) (or extra-European)o International Laboratory Accreditation Cooperation (ILAC)

• National metrological institutes (NMI)

The reference standard instrument should still have a measurement uncertainty of typically better than one-third of thenominal uncertainty of the calibrated instrument (see point 10).




GENERAL GUIDELINES

30

Technical PersonnelTechnical personnel should be specifically trained and operating under the technical and management proceduresregarding the quality manual of the company or the laboratory.

Operating Procedures The operating calibration procedures should be specifically drawn up:

• For each type of provided measurement• For each type of instrumentation with respect to any applicable normatives

In the absence of specific reference normatives, it is good practice to follow the generic operating proceduresdescribed in table 6-1.

6.3 Generic Operational Procedures3

Among the various international normatives available in the field of instrumentation, reference is made hereinafter toIEC 61298 concerning the methods and procedures to evaluate process instrumentation. It provides for the accuracydetermination, namely the error indication, of industrial measurement instrumentation (i.e., pressure, flow, level,temperature). There are essentially two main procedures: calibration and verification.

6.3.1 Calibration Procedure (or Initial Characterization)This is applicable to new instrumentation, and typically also to the standard instrumentation. This first procedureconsists initially in performing three full excursions of the measuring signal up and down, and then follow thismethodology:

a. With input signal of 0%, adjust the initial scale of the instrument being calibrated.b. With input signal equal to 100%, adjust the full scale of the instrument being calibrated.c. Return the input signal to 0%, and check the instrument’s output signal. If this error is more than one-quarter

error of the nominal value specified by the manufacturer or the user of the instrument, readjust the initial scale to fall within the tolerance above.

d. Return the input signal to 100% and check the instrument’s output signal. If this error is more than one-quarter error of the nominal value specified by the manufacturer or the user of the instrument, readjust the full scale up to fall within the tolerance above.

e. Repeat steps (c) and (d) until the initial and the full scale are within the tolerance of one-quarter specified nominal value.

f. Perform the measuring cycle every 20–25% by detecting the instrument output signal, after a sufficient period of stabilization, in the following modes:

• 20/40/60/80/100/80/60/40/20/0%• 25/50/75/100/75/50/25/0%

Usually the complete measuring cycle up and down is expected for instrumentation using sensors at “elasticdeformation” (and therefore with displacement: type dial manometers or dilatation thermometers) while a measuringcycle is carried out up (preferentially) or down for the instrumentation using sensors at the “solid state” (and thus usingsensors without moving, electric type: digital multimeters and sensor thermoelectrics as resistance thermometers andthermocouples that don’t have inherent hysteresis phenomena).

3. See also table 6-3




31

Table 6-1. Main Terms Relating to Measurement Processes (ISO-VIM)

Measurand:Quantity intended to be measured.

Measurement:Process of experimentally obtaining one or more quantity values that can reasonably be attributed to a quantity.

Error:Measured quantity value minus a reference quantity value.

Accuracy:Closeness of agreement between a measured quantity value and a true quantity value of a measurand.

Accuracy class:Class of measuring instruments or measuring systems that meet stated metrological requirements that are intended to keepmeasurement errors or instrumental measurement uncertainties within specified limits under specified operating conditions.

Measurement accuracy:Closeness of agreement between a measured quantity value and a true quantity value of a measurand.

International measurement standard:Measurement standard recognized by signatories to an international agreement and intended to serve worldwide.

Reference measurement standard:Measurement standard designated for the calibration of other measurement standards for quantities of a given kind in a givenorganization or at a given location.

Traveling measurement standard:Measurement standard, sometimes of special construction, intended for transport between different locations.

Primary measurement standard:Measurement standard established using a primary reference measurement procedure, or created as an artifact, chosen byconvention.

Secondary measurement standard:Measurement standard established through calibration with respect to a primary measurement standard for a quantity of thesame kind.

Material measure:Measuring instrument reproducing or supplying, in a permanent manner during its use, quantities of one or more given kinds,each with an assigned quantity value.

Reference material:Material, sufficiently homogeneous and stable with reference to specified properties, that has been established to be fit for itsintended use in measurement or in examination of nominal properties.

Measuring instrument:Device used for making measurements, alone or in conjunction with one or more supplementary devices.

Metrological traceability:Property of a measurement result whereby the result can be related to a reference through a documented unbroken chain ofcalibrations, each contributing to the measurement uncertainty (see point 4.2).

Metrological traceability chain:Sequence of measurement standards and calibrations used to relate a measurement result to a reference (see figure 4-1).

Measurement uncertainty:Nonnegative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on theinformation used (for more details, see point 5 and table 5-1).

Measurement method:Generic description of a logical organization of operations used in a measurement. Measurement methods may be qualified invarious ways, such as:

• Direct measurement method (e.g., manometer calibration with pressure balance)• Indirect measurement method (e.g., manometer calibration with reference manometer)



GENERAL GUIDELINES

32

6.3.2 Verification Procedure (or Metrological Confirmation)The verification procedure is applicable to instrumentation in operation and therefore particularly suitable for themetrological confirmation of instrumentation in production processes.

This second procedure also begins by executing three complete excursions of the measurement signal up and down;expected, however, only for mechanical-type instrumentation with displacement sensors.

Subsequently, however, it only provides for the execution of the measuring cycle according to the method described inthe preceding calibration procedure in step (f), since the aim of this procedure is to be seen during the metrologicalconfirmation in subsequent times, if the error or uncertainty detected on the instrumentation of the production processis better than the limit expected for the “correct control” of the quality of the “measurement process.”

6.4 General Index of the Operational Procedures

Each operating procedure should be structured on the following points:

1. Scope and purpose2. Identification and classification3. Normative references4. Ambient conditions5. Initial checks6. Calibration method7. Calibration verification8. Calibration results9. Metrological confirmation

The last point is required only in the case of procedures aimed at metrological confirmation.

6.5 General Index of the Calibration Report or Metrological Confirmation4

Following the calibration procedure or metrological confirmation, note and record the results and further elaborations,on a specific report that must contain at least the following information (see also ISO 10012):

a. Applicant (if applicable)b. Subject of the report (calibration or confirmation)c. Name or symbol of the instrumentd. Reference standards and calibration certificatese. Procedures usedf. Ambient conditionsg. Reference values and measured errorsh. Measurement uncertainty resultingi. Uncertainties of measurement requestsj. The result of the declaration of conformityk. Execution date of the calibration or confirmation and date of the next confirmationl. Signature executor and the person responsible for the calibration or confirmation reports

For an example of procedures and reports of calibration or confirmation, see Part II.

4. See also table 6-3




33

6.6 Examination of Internal or External Calibration Feasibility of Measuring Instruments

In order to properly calibrate instruments at home, in the first analysis, a company must have at least the followingelements:

• A metrological chain, composed of at least one standard, for each type of instrument• Any ancillary equipment, according to requirements (e.g., generators, furnaces)• A local or a work area with suitable environmental conditions to the needs• Designed and tested calibration procedures • Trained and qualified personnel

All this represents a significant cost that can be justified by the amount of equipment to be calibrated, and therefore acost/benefit analysis on the convenience of equipping a laboratory or on delegating calibration to an external laboratorymust be done.

Generally, for instruments such as manometers, thermometers, hygrometers, micrometers, calipers, and analog anddigital multimeters, internal calibration is convenient when the group of instruments is referable to a single referencestandard that exceeds at least 10 units. For lesser quantities, it may be more beneficial to contact an externallaboratory.

These figures and tables provide examples:

• Figure 6-1 shows a possible suitable framework to analyze the possibility of internal or external calibration.• Table 6-2 shows the possible advantages and disadvantages of internal and external calibration.• Table 6-3 shows some considerations for the procedures and results of related expressions.

Figure 6-1. Sequential Scheme of Analysis for Choice of the Internal or External Calibration

Accreditedalibration

enter?NOTYES

NOTYES

DEFINITION OF THE QUALITY PLANAND PRODUCT CHARACTERISTICS

TO CHECK

Calibrationinside theompany ?

IDENTIFICATION OF THE INSTRUMENTSTHAT MUST BE CALIBRATED

Qualifythe alibration

enter

RESULTS CONTROL (MADE IN COMPANY)

check that the results are within acceptance criteria

indicate the controller ( aboratory or uality esponsible)

Calibration at a alibration enter:ILAC, EA, etc.

Calibration at aqualified outside center

Calibration in theinternal metrological

laboratory



GENERAL GUIDELINES

34

Table 6-2. Evaluation of the Advantages and Disadvantages of Internal and External Calibration

Evaluation Internal Calibration External Calibration

Purchase costs of the reference standards Yes No

Calibration of the reference standards Yes No

Cost for personnel training Yes No

Cost of procedures Yes No

Locations for the laboratory Yes No

Unavailability time of the instrument hour 2-30 days

Costs to ship the instrument No Yes

Possibility of damage during transport No Yes

Possibility of immediate verifications Yes No

Possibility of checks on the processes Yes No

Laboratory qualification No Yes, if it is not ILAC

Table 6-3. Common Terms Relating Procedures and Results of Expressions (ISO and Others)

Operational procedure:Procedure that tends to define and characterize the metrological characteristics of an instrument, or to adjust or restore thefunctional and metrological characteristics of an instrument or a measuring apparatus. Note: The operational procedure should be specified: measurement, calibration, verification, etc.

Measurement procedure:Detailed description of a measurement according to one or more measurement principles and to a given measurement method,based on a measurement model and including any calculation to obtain measurement results.

Calibration procedure:Procedure performed under the specified conditions that establishes the relationship between the values of a quantity relatedwith the associated measurement uncertainties and the reading of a measuring instrument, which can be expressed by meansof a table or calibration curve, usable for the eventual measurement results correction conducted with the calibrated instrument.Note: This procedure should not be confused with the procedures described below!

Verification procedure:Operation that provides evidence that an instrument meets the specified requirements. (Note: This procedure is normally used inthe sense of “metrological confirmation.”)

Adjustment procedure:Set of operations carried out (of zero and span adjustments) on an instrument so that it provides prescribed information(specified) in relation to the measured value. Note: This procedure is commonly used before the “calibration procedure.”

Maintenance procedure:Process conducted in a systematic manner or as necessary to return the instrument to its normal functional conditions. (Note:This procedure is performed periodically according to the manufacturer’s specifications.)

Calibration curve:Expression of the relation between indication and corresponding measured quantity value (and relative measurementuncertainty).

Calibration certificate:Document that provides a calibration curve of an instrument, issued by a laboratory or an accredited organization (e.g.,accredited ISO 17025: ILAC, EA).

Calibration report:Document that provides a calibration curve of an instrument, issued by a laboratory or an organization that is not accredited forcalibration (e.g., accredited only ISO 9001).

As found report/certificate:Document that provides a calibration curve for an instrument, as found, or as presented to the calibration or metrologicalconfirmation.

As left report/certificate:Document that provides a calibration curve for an instrument, as left, or after making an adjustment procedure (because it wasfound out of the specifications).




REQUIREMENTS IN THE QUALITY MANAGEMENT SYSTEMS ISO 9001, 14001, 16949, AND EN 9100

35

7 Requirements in the Quality Management Systems ISO 9001, 14001, 16949, and EN 9100

7.1 Introduction

The main international normative requirements on calibration of measuring instruments in the quality managementsystems, in the environmental management system, and in the automotive and aeronautic industries are provided.

7.2 ISO 9001 Requirements

ISO 9001:2015 on quality management systems (QMS) states in point 7.1.5:

7.1.5 Monitoring and measuring resources

7.1.5.1 GeneralThe organization shall determine and provide the resources needed to ensure valid and reliable results whenmonitoring or measuring is used to verify the conformity of products and services to requirements.

The organization shall ensure that the resources provided:

a) Are suitable for the specific type of monitoring and measurement activities being undertakenb) Are maintained to ensure their continuing fitness for their purpose

The organization shall retain appropriate documented information as evidence of fitness for the purpose ofmonitoring and measurement resources.

7.1.5.2 Measurement traceabilityWhen measurement traceability is a requirement, or is considered by the organization to be an essential part ofproviding confidence in the validity of measurement results, measuring equipment shall be:

a) Calibrated or verified, or both, at specified intervals, or prior to use, against measurement standardstraceable to international or national measurement standards; when no such standards exist, the basisused for calibration or verification shall be retained as documented information

b) Identified in order to determine their statusc) Safeguarded from adjustments, damage, or deterioration that would invalidate the calibration status and

subsequent measurement results

The organization shall determine if the validity of previous measurement results has been adversely affected whenmeasuring equipment is found to be unfit for its intended purpose, and shall take appropriate action as necessary.

7.3 ISO 14001 Requirements

ISO 14001:2015 on environmental management systems (EMS) states in point 9.1.1:

9.1 Monitoring, measurement, analysis, and evaluation

9.1.1 General

The organization shall monitor, measure, analyze, and evaluate its environmental performance. The organizationshall determine:

a) What needs to be monitored and measuredb) The methods for monitoring, measurement, analysis, and evaluation, as applicable, to ensure valid resultsc) The criteria by which the organization will evaluate its environmental performance, and appropriate

indicatorsd) When the monitoring and measuring shall be performede) When the results from monitoring and measurement shall be analyzed and evaluated



Part II

Requirements and Criteria for the Management and Calibration of Measuring Instruments

Part II describes the requirements and operating procedures for the management and calibration of measuring instruments for thefollowing measurement quantities:

1.0 Physical quantities: Pressure, flow, level, temperature, etc.

2.0 Chemicals for liquids: pH, redox, turbidity, conductivity, etc.

3.0 Chemicals for gases: Infrareds, ultraviolets, gas chromatographs, etc.

4.0 Mechanical quantities: Length, speed, acceleration, etc.

5.0 Electrical quantities: Indicators, oscilloscopes, multimeters, etc.

For the main types of measuring instruments, the operating procedures of calibration and metrological confirmation for managing thequality of the measurements is presented. They are accompanied by the registry and metrology card, suitable for recording theinstrument identification and the registration of subsequent verification checks and metrological confirmation implemented with thetwo methods explained in Part I, 10.2.1 and 10.2.2:

• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to the Maximum Tolerated Error(MTE). This is generally recommended when using references with uncertainty less than or equal to one-third of that of theinstrument to be calibrated.

• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the Maximum ToleratedUncertainty (MTU). This is particularly recommended when using references with uncertainty greater than one-third of thatof the instrument to be calibrated.

Obviously, this must always be done in compliance with any applicable normative references.

At the same time, note that errors and uncertainties are generally expressed:

• In absolute terms in the case of temperatures (°C), lengths (mm), etc.• In relative terms (e.g., percent of full scale for pressure or percent of reading for flow)

Also note that for editorial convenience, all metrological confirmation intervals of different measurement instruments have been setat one year, without regard to the course management criteria of the intervals reported in Part I in:

• 8.5 Definition of Metrological Confirmation Intervals• 8.6 Review of the Metrological Confirmation Intervals• 8.7 Examples of Definition of Metrological Confirmation Intervals

This is unless otherwise specified in any technical requirements or related legislations.

In addition, it points out the importance of reviewing the metrological confirmation intervals with the scale method provided by theinternational document OIML D 10, which in principle should lead to:

• An increase in the interval for the most stable instruments (or scarcely used), type: manometers, thermocouples, etc.• A decrease in the interval for the most critical instruments (or continuous use), type: analyzers, gas chromatographs, etc.

This is unless otherwise specified in the technical requirements and/or related legislations.

Finally, note that for uniformity in the various operating procedures, the document has highlighted the environmental conditions interms of temperature, relative humidity, and atmospheric pressure. This is a practice for a proper independent laboratory. For anindustrial laboratory, always specify the temperature, and specify humidity and pressure if they are influential or prescribed byapplicable normative references.



INTRODUCTION

73

1. Physical Quantities

This first section of Part II describes the requirements and specific criteria for managing and calibrating measuring instruments ofphysical quantities:

1.1 Pressure1.2 Flow1.3 Level1.4 Temperature1.5 Humidity1.6 Viscosity1.7 Density1.8 Mass

For each quantity, the International System (SI) of units, any specific definitions, the main operating principles, and any referencetables will be succinctly presented.

In addition to the main types of instruments, the handbook will present the relative operating procedure of calibration andmetrological confirmation articulated on the following points:

1. Scope and Purpose2. Identification and Classification3. Normative References4. Ambient Conditions5. Initial Checks6. Calibration Method7. Calibration Verification8. Calibration Results9. Metrological Confirmation



PRESSURE

75

1.1 Pressure

Units of Measurement and Definitions

The pressure P is defined as the ratio between the force F acting on a surface and its area A:

P = F / A

The pressure unit in the International System is pascal (Pa):

1 Pa = 1 N / 1 m2

The pressure unit bar is also accepted:

1 bar = 105 Pa

For the relationship with other units, see table 1.

Notes: The standard reference atmospheric pressure at sea level is 1013.25 mbar (101325 Pa). The air pressure decreases byabout 1 mbar for every 10 m above sea level (valid until 4000 m).

The concepts related to the type of the relative and absolute pressures are shown in figure 1.

Table 1. Conversions of the Different Units of Pressure

Pa bar Atm kg/cm2 mm H2O@ 4°C

mm Hg@ 0°C

psiin H2O@ 4°C

in Hg@ 0°C

1 Pa 1 0.00001 0.0000099 0.000010 0.101972 0.00750 0.000145 0.004015 0.000295

1 bar 100000 1 0.986923 1.01972 10197.2 750.062 14.5038 401.463 29.530

1 Atm 101325 1.01325 1 1.03323 10332.3 760 14.6959 406.78 29.921

1 kg/cm2 98066.5 0.980665 0.967841 1 10000 735.559 14,2233 393.701 28.959

1 mm H2O 9.80665 0.000098 0.000097 0.0001 1 0.07355 0.001422 0.03937 0.002896

1 mm Hg 133.322 0.001333 0.001316 0.001359 13.595 1 0.019337 0.53524 0.03937

1 psi 6894.76 0.068947 0.068046 0.070307 703.07 51.715 1 27.68 2.03602

1 in H2O 249.089 0.002491 0.002458 0.002540 25.4 1.86832 0.03613 1 0.073556

1 in Hg 3386.39 0.038639 0.033421 0.034532 345.316 25.4 0.491154 13.5951 1

Figure 1. Concepts Related to the Type of Pressure Measurement

Pressure [bar]

1.013

0

Atmospheric pressure

Absolute pressure above atmospheric P

Related pressure below atmospheric P

(depression)

Limits of variation of atmospheric pressure Absolute pressure

below atmospheric P

Related pressure above atmospheric P

(pressure)



PHYSICAL QUANTITIES

76

Main Instruments for Pressure Measurement

The main instruments and most common pressure measurements are as follows:

• Manometers or pressure gauges, according to European standard EN 837• Transmitters or pressure transducers, according to international standard IEC 60770

As an example, the following tables show the features provided by the European standard EN 837 for manometers (i.e., pressuregauges or dial gauges), which standardizes the use of Bourdon tubes, membranes, and capsules: table 2 for standard ranges, table3 for standard nominal diameters, and table 4 for standard accuracy classes.

Notes:(1) The preferred units are the bar and mbar.(2) The maximum measuring range is 25 bar for diaphragm and capsule manometers.(3) Measuring ranges are in mbar only for diaphragm and capsule manometers.

Table 2. Standard Measuring Ranges for Manometers (EN 837)

Instrument Measuring Ranges (1)

Manometers orPressure Gauges

Measuring ranges in bar (2)0 – 0.60 – 1 0 – 10 0 – 100 0 – 10000 – 1.6 0 – 16 0 – 160 0 – 16000 – 2.5 0 – 25 0 – 2500 – 4 0 – 40 0 – 4000 – 6 0 – 60 0 – 600

Measuring ranges in mbar (3)0 – 1 0 – 10 0 – 1000 – 1.6 0 – 16 0 – 1600 – 2.5 0 – 25 0 – 2500 – 4 0 – 40 0 – 4000 – 6 0 – 60 0 – 600

Vacuum Gauges Measuring ranges in bar–0.6 – 0 –1 – 0

Measuring ranges in mbar (3)–1 – 0 –10 – 0 –100 – 0–1.6 – 0 –16 – 0 –160 – 0–2.5 – 0 –25 – 0 –250 – 0–4 – 0 –40 – 0 –400 – 0–6 – 0 –60 – 0 –600 – 0

Pressure and Vacuum Gauges Measuring ranges in bar–1 – 0.6 –1 – 3 –1 – 9 –1 – 24–1 – 1.5 –1 – 5 –1 – 15




PRESSURE

77

Note:(1) The minimum nominal diameter is 50 for diaphragm and capsule manometers.

Note:(1) The minimum accuracy class is 0.6 for diaphragm and capsule manometers.

Calibration and Metrological Confirmation Procedures

1.1.1 Pressure indicators (manometers) : PI : EN 837

1.1.2 Pressure transmitters : PT : EN 60770

1.1.3 Electromechanical manometers : PE : EURAMET 17

1.1.4 Pressure balances : PB : EURAMET 3

For Other Pressure Gauges

• Manometers for extinguishers use : EN 3-5 with accuracy class 6%• Manometers for welding use : EN 562 with accuracy class 2.5%• Manometers for medical use : EN 738 with accuracy class 2.5%• Manometers for tires use (1) : EN 12645 according to EC Directive 86/217 (with MTE ≤ 2.5%)• Manometers for pressure blood (2) : EN 1060 according to EC Directive 93/42 (with MTE ≤ 3 mm Hg)

For the latter pressure gauges, generally follow the procedure for manometers EN 837 (1.1.1) with calibration points at least every20% (15% for EN 562); however, follow the specific method described in the relevant technical normative references or legalregulations.

Notes:(1) There is also a similar international recommendation, OIML R 23: Tire pressure gauges for motor vehicles.(2) There is also a similar international recommendation, OIML R 16: Sphygmomanometers.

Table 3. Standard Nominal Diameters DN for Manometers (EN 837)

DN Nominal Diameters (1)

(mm) 40 50 63 80 100 150 160 250

Table 4. Standard Accuracy Classes for Manometers (EN 837)

Cl Accuracy Classes (1)

(%) 0.1 0.25 0.6 1 1.6 2.5 4



PHYSICAL QUANTITIES

78

1.1.1 Pressure Indicators

1. Scope and PurposeThis procedure applies to all types of pressure indicators or dial manometers with Bourdon tubes or membranes and capsules, withmeasuring ranges between –1 and 1600 bar (or greater).

2. Identification and ClassificationBefore information about the new instrument is used in the application, it must be filed in accordance with the instrument card at theright, defining the procedures, the normative references, and the required checks and results. The instrument must be confirmedmetrologically for the application, including the instrument’s recalibration, if necessary.

3. Normative References• EN 472 (1995) : Pressure gauges – vocabulary• EN 837-1-2-3 (1996) : Pressure gauges – Bourdon tube, membrane, capsule pressure gauges

4. Ambient ConditionsTemperature: (20 ± 2)°C, Relative humidity: (50 ± 25)%, Atmospheric pressure: (1000 ± 25) mbar

5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such asmeasuring scale and fittings. Then install the instrument in the measuring circuit, ensure that there are no leaks, and make threepreload cycles on the whole verification range.

6. Calibration MethodPerform calibration methods by comparing with standard instruments:

• For laboratory manometers, by pressure balance with standard masses (figure A)• For industrial manometers with accuracy class more than 1, with standard manometer (figure B)• For industrial manometers with accuracy class less than 1, with standard calibrator (figure C)

It has a lower measurement uncertainty, possibly one-fourth of that of the manometer in calibration (according to the normativereferences).

If there is a different level Δh between the intake of the standard manometer and the manometer in calibration, it is necessary tocorrect the pressure difference ΔP between the two levels, through the relation: ΔP = ρ ⋅ g ⋅ Δh [Pa], where ΔP = differential pressurein pascal (1 Pa = 10-5 bar), ρ = density of the measurement fluid (for water ≈ 1000 kg/m3), g = local gravitational acceleration (orstandard = 9.80665 m/s2), and Δh = different level between the two manometers in meters

7. Calibration VerificationThe verification should be carried out with increasing/decreasing pressure (i.e., at least every 25% of scale):

25 – 50 – 75 – 100 – 75 – 50 – 25 – 0%Reach every point of measurement without going over, and wait for the indication that the standard and instrument in calibration areperfectly stable. Then read and detect the standard and the instrument indications.

8. Calibration ResultsReport the calibration results in an instrument card to first be processed and then valued against the Maximum Tolerated Error(MTE) or Maximum Tolerated Uncertainty (MTU):

• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to MTE.• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the MTU.

If the check is not positive, it will be necessary to recalibrate the instrument, and then repeat the calibration verification (point 7), ordowngrade or alienate the instrument.

9. Metrological ConfirmationRecord on the side of the instrument card:

• The results of the metrological confirmation (positive, negative: declassification or alienation)• The signature of those who made the verification and the next verification date

Also, fill out and attach the positive confirmation label on the instrument, indicating at least the number of the verification/calibrationreport, the instrument serial number, and the next verification date.

Figure A Figure B Figure C

Standard manometer Manometer in calibration

Manual pump or pressure reducer

Δh = 0

Manometer in cal ibration

Standard ca librator Reference leve l

2.500 bar Δh ≠ 0

kPa

43

2

6

5 1

0

Variable volume

Fluid reservoir

Fluid filling valve

Mass Manometer in calibration



PRESSURE

79

Metrological Laboratory

Pressure Indicators(pressure gauges or dial manometers)

Card Number XX-PI

IDENTIFICATION AND METROLOGICAL DATA

Instrument identification PI 11 Measuring range 0–10 barInstrument classification Process Calibration range 0–10 barInstrument denomination Manometer Accuracy class 1%Manufacturer ABC Measure resolution (Eres) 0.05 barModel DN 100 Max Tolerated Error (MTE) 0.10 barSerial number XYZ Max Tolerated Uncertainty (MTU) 0.15 barDate of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.01 barLocation of installation Process PI 11 Certificate number of standard 1111Installation conditions Vertical Fluid exercise/calibration Air/airUtilization conditions Eventual Fluid filling Eventual

APPLICABLE PROCEDURES AND NORMATIVES

Calibration procedure PP-PI Maintenance procedure Manufacturer spec.Confirmation procedure PP-PI Normative reference EN 837

REQUIRED CONTROLS

Calibration YES NO

Confirmation YES NO

Certification YES NO

Body Control Internal External

TRACEABILITY OF MEASUREMENT

Calibration and ConfirmationInternal traceability to reference standard PS 11

CertificationExternal traceability of certification body

INTERVAL OF METROLOGICAL CONFIRMATION

3 months 6 months 1 year 2 years

RESULTS OF CONFIRMATION

Date of Control

Body Control

Number ofReport

Results of Confirmation

DriftMRE/bar

Signature Vision

Deadline Notes

01.06.2017 Internal XX-PI Positive 0.05 White 01.06.2018

RESULTS OF LAST CONFIRMATION

Was the adjustment made before the verification? YES NO

PressureReference

(bar)

RELIEVED VALUES RELIEVED ERRORS Max Relieved Error

Emax(bar)

Increasing Decreasing Increasing Decreasing

(bar) (bar) (bar) (bar)

0 – 0.05 – 0.052 1.95 2.05 –0.05 0.054 3.95 4.05 –0.05 0.05 0.056 5.95 6.05 –0.05 0.058 7.95 8.05 –0.05 0.0510 9.95 – –0.05 –

RESULTS OF METROLOGICAL CONFIRMATION

MRE < MTE 0.05 bar < 0.10 bar YES NOOR ALTERNATIVELY

MRU < MTU YES NO

THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018

MetrologicalFunction

EXECUTOR SIGNATURE RESPONSIBLE SIGNATURE DATE 01.06.2017

barbarEresEUref

MRU 15.006.046,305.0

73.105.0

201.02

3.23max

22

222222

<=

+

+

⋅=

+

+

⋅=



LEVEL

113

1.3 Level


The level of liquid and solid products (such as powders, mixtures, and granules) in containers (such as tanks, silos, and vessels) ismeasured in height in meters. In the case of liquids, the level or height measurement is always the effective real average height ofthe liquid content. In the case of solids, the level or height measured is the punctual real actual height of the solid content, a heightwhich is substantially a function of the measuring point (figure 1).


1.3.1 Pressure (Hydrostatic) : LP: IEC 60770

1.3.2 Reflection (Sonar and Radar) : LX: IEC 60770

Figure 1. Level Measurement of Products in Containers with Sensors (1-2-3) Mounted on Top of the Tanka. Level measurement of liquids: The sensors always detect the same level h (h1 = h2 = h3) given the horizontal liquid level.b. Level measurement of solids: The sensors detect various levels (h1 ≠ h2 ≠ h3) as a function of the content solid surface.

1 2 3 1 2 3

h h1 h2 h3

(a) (b)



PHYSICAL QUANTITIES

114

1.3.1 Measurers at Pressure (Hydrostatics)

1. Scope and PurposeThis procedure applies to the types of pressure level meters, otherwise called hydrostatic, that use relative (for vessels open to theatmosphere) or differential (for pressure vessels) pressure measuring instruments with an analog (mA or mV) or digital (HART orBus) output signal.


3. Normative References• IEC 60770-1 (2010) : Industrial transmitters – Part 1: Methods for performance evaluation• IEC 60770-2 (2010) : Industrial transmitters – Part 2: Methods for inspection and routine• IEC 60770-3 (2014) : Industrial transmitters – Part 3: Methods for performance evaluation of intelligent transmitters


5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such ascasings, fittings, and the optional indicator. Then install the instrument in the measuring circuit and ensure that there are no leaks.Make three preload cycles on the whole verification range.

6. Calibration MethodSince the principle of hydrostatic measurement precisely uses the pressure generated by the liquid level in the vessel bottom(according to the note and detailed formula at the bottom of a typical installation in figure A) to perform the calibration locally (byintercepting the transmitter) or elsewhere (by removing the transmitter) for comparison with a standard instrument (calibrators orpressure balances):

• For analog instruments with a pressure calibrator measuring the output signal (figure B)• For digital instruments with a pressure calibrator and digital communicator or configurator (figure C)

In any case, it has a lower measurement uncertainty possibly of one-fourth of that of the instrument in calibration (according to thenormative references).

The hydrostatic pressure exerted by the liquid level of the tank bottom is given by the following relation: P = ρ ⋅ g ⋅ h [Pa], where P =pressure exercised in pascal (1 Pa = 10-5 bar), ρ = density of the measurement fluid (for water ≈ 1000 kg/m3), g = local gravitationalacceleration (or standard = 9.80665 m/s2), h = level height to be measured in meters

7. Calibration VerificationThe verification should be carried out with increasing/decreasing pressure (i.e., at least every 20% of scale):

20 – 40 – 60 – 80 – 100 – 80 – 60 – 40 – 20 – 0%Reach every point of measurement without going over, wait for the indication that the standard and instrument in calibration areperfectly stable, then read and detect the standard and the instrument output or indications.


• Verify that the Maximum Relieved Error (MRE) of the instrument is less than or equal to the MTE.• Verify that the Maximum Relieved Uncertainty (MRU) of the instrument is less than or equal to the MTU.

If the check is not positive, it will be necessary to recalibrate the instrument, then repeat the calibration verification (point 7), ordowngrade or alienate the instrument.




Figure A Figure B Figure C

Output4-20 mA

SupplyConnection

Load250 Ω

Communicatoror ConfiguratorTransmitter

or Transducer




LEVEL

115


Measurers at Pressure(Hydrostatics)

Card Number XX-LP

IDENTIFICATION AND METROLOGICAL DATAInstrument identification LP 11 Measuring range (0–10m H2O) 0–100 kPaInstrument classification Process Calibration range (0–10m H2O) 0–100 kPaInstrument denomination Transmitter Accuracy class 0.05%Manufacturer ABC Measure resolution (Eres) 0.01%Model LP Max Tolerated Error (MTE) 0.05%Serial number XYZ Max Tolerated Uncertainty (MTU) 0.10%Date of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.01%Location of installation Process LP 11 Certificate number of standard 1111Installation conditions Vertical Fluid exercise/calibration Water/airSupply conditions Nominal ± 1% Output load 250 Ω ± 0.1%

APPLICABLE PROCEDURES AND NORMATIVES Calibration procedure PP-LP Maintenance procedure Manufacturer spec.Confirmation procedure PP-LP Normative reference IEC 60770

REQUIRED CONTROLSCalibration

YES NOConfirmation

YES NOCertification

YES NOBody Control

Internal ExternalTRACEABILITY OF MEASUREMENT

Calibration and ConfirmationInternal traceability to reference standard PS 11


INTERVAL OF METROLOGICAL CONFIRMATION 3 months 6 months 1 year 2 years

RESULTS OF CONFIRMATIONDate of Control

Body Control

Number ofReport


DriftMRE/%

Signature Vision

Deadline Notes

01.06.2017 Internal XX-LP Positive 0.03 White 01.06.2018

RESULTS OF LAST CONFIRMATIONWas the adjustment made before the verification? YES NO

PressureReference

(%)

RELIEVED VALUES RELIEVED ERRORS Max Relieved Error

Emax(%)

Increasing Decreasing Increasing Decreasing(%) (%) (%) (%)

0 – 0.00 – 020 19.99 20.01 – 0.01 0.0140 39.98 40.00 – 0.02 0.00 0.0360 59.97 59.99 – 0.03 – 0.0180 79.98 80.00 – 0.02 0.00

100 99.99 – – 0.01 –RESULTS OF METROLOGICAL CONFIRMATION

MRE < MTE 0.03% < 0.05% YES NOOR ALTERNATIVELY

MRU < MTU YES NO

THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018MetrologicalFunction

EXECUTOR SIGNATURE RESPONSIBLE SIGNATURE DATE01.06.2017

%10.0%04.046.301.0

73.103.0

201.02

3.23max

22

222222

<=

+

+

⋅=

+

+

⋅= EresEUref

MRU



PHYSICAL QUANTITIES

116

1.3.2 Measurers at Reflection (Sonar and Radar)

1. Scope and PurposeThis procedure applies to all the types of level measurers at reflection (sonar and radar) with an analog (mA or mV) or digital (HARTor Bus) output signal and a measurement range to 50 m (or more).


3. Normative References• IEC 60770-1 (2010) : Industrial transmitters – Part 1: Methods for performance evaluation• IEC 60770-2 (2010) : Industrial transmitters – Part 2: Methods for inspection and routine • IEC 60770-3 (2014) : Industrial transmitters – Part 3: Methods for performance evaluation of intelligent transmitters


5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such ascasings, fittings, and the optional indicator. Then install the instrument in the measurement system and check the electricalfunctionality.

6. Calibration MethodSince the measuring principle of the transmitters in question uses the reflection of waves, use, respectively:

• Sonic for sonar, with propagation velocity of about 300 m/s• Electromagnetic for radar, with velocity of propagation of about 300 • 106 m/s

Therefore, it must be prepared in a “variable level” calibration system in order to verify the measurements obtained by thetransmitters with respect to the calibration system, or between the probe and the level surface.

The calibration, therefore, can be practically performed (see the figure) locally, by intercepting the transmitter, or remotely, byremoving the transmitter. This is provided that this last condition is representative of the process (type of gas, pressure, andtemperature) in terms of the wave propagation speed of measurement and the quality of the reflection, for comparison with standardsystems consisting of ribs or reference lasers, having in each case a lower measurement uncertainty possibly of ¼ of that of theinstrument being calibrated (according to the normative references).

7. Calibration VerificationThe verification must be carried out with progressive levels every 20% of the measuring scale, namely:

0 – 20 – 40 – 60 – 80 – 100%.



If the check is not positive, it will be necessary to recalibrate the instrument, then repeat the calibration verification (point 7), ordowngrade or alienate the instrument.




Depth of the level to be measured

Variable level to be measured

Max level (100%)

Reference level to be measured by comparison with rib metric or laser device

Min level (0%)

Measure wave

Reflected wave



LEVEL

117


Measurers at Reflection(sonar and radar)

Card Number XX-LR

IDENTIFICATION AND METROLOGICAL DATAInstrument identification LR 11 Measuring range (0–10m H2O) 0–10 mInstrument classification Process Calibration range (0–10m H2O) 0–10 mInstrument denomination Transmitter Accuracy class 0.05%Manufacturer ABC Measure resolution (Eres) 0.01%Model LR Max Tolerated Error (MTE) 0.05%Serial number XYZ Max Tolerated Uncertainty (MTU) 0.10%Date of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.01%Location of installation Process LR 11 Certificate number of standard 1111Installation conditions Vertical Fluid exercise/calibration Water/waterSupply conditions Nominal ± 1% Output load 250 Ω ± 0.1%

APPLICABLE PROCEDURES AND NORMATIVES Calibration procedure PP-LR Maintenance procedure Manufacturer spec.Confirmation procedure PP-LR Normative reference IEC 60770

REQUIRED CONTROLSCalibration

YES NOConfirmation

YES NOCertification

YES NOBody Control

Internal ExternalTRACEABILITY OF MEASUREMENT

Calibration and ConfirmationInternal traceability to reference standard LS 11


INTERVAL OF METROLOGICAL CONFIRMATION 3 months 6 months 1 year 2 years

RESULTS OF CONFIRMATIONDate of Control

Body Control

Number ofReport


DriftMRE/%

Signature Vision

Deadline Notes

01.06.2017 Internal XX-LR Positive 0.03 White 01.06.2018

RESULTS OF LAST CONFIRMATIONWas the adjustment made before the verification? YES NO

LevelReference

(m)

RELIEVED VALUES RELIEVED ERRORS Max Relieved ErrorEmax(%) (m) (%)

0 0.000 0.002 1.999 – 0.014 3.998 – 0.02 0.036 5.997 – 0.038 7.998 – 0.0210 9.999 – 0.01

RESULTS OF METROLOGICAL CONFIRMATIONMRE < MTE 0.03% < 0.05% YES NO

OR ALTERNATIVELYMRU < MTU YES NO

THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018MetrologicalFunction


%10.0%04.046.301.0

73.103.0

201.02

3.23max

22

222222

<=

+

+

⋅=

+

+

⋅= EresEUref

MRU



TEMPERATURE

119

1.4 TEMPERATURE


The kelvin is the fraction 1/273.16 of the temperature interval from the triple point of water to absolute zero, and can be formulatedas follows:

1 K = 1/273.16 Thermodynamic temperature of the triple point of water

For conversion to other units still in use and for the evolution of the temperature scale, see table 1 and table 2. (Please note that fortemperature intervals, the kelvin K corresponds to the °C.)

• tC = Relative temperature in Celsius degrees (°C): Scale that assigns 0°C and ≅ 100°C at the fusion and boiling point of thewater

• tK = Absolute temperature in kelvin (K): Scale that assigns 0 K = –273.15°C at zero absolute temperature• tF = Relative temperature in Fahrenheit degrees (°F): Scale that assigns 32°F and ≅ 212°F at the fusion and boiling point of the

water• tK = Absolute temperature in Rankine degrees (°R): Scale that assigns 0°R = –459.67°F at zero absolute temperature

(1) Primary fixed point not provided(2) Secondary fixed point providedFor the old International Practice Temperature Scale, IPTS 68 (1968)For the new International Temperature Scale, ITS 90 (1990)

Table 1. Conversion for Temperature Measurement Units

Temperature tC tK tF tR

tC 1 tK – 273.15 5/9 (tF – 32) 5/9 tR – 273.15

tK tC + 273.15 1 5/9 tF + 255.37 5/9 tR

tF 9/5 tC + 32 9/5 tK – 459.67 1 tR – 459.67

tR 9/5 tC + 491.67 9/5 tK tF + 459.67 1

Table 2. Fixed Points of the International Temperature Scales

Substance Fixed Points(@ 101325 Pa)

IPTS 68 ITS 90

Element Symbol (K) (°C) (K) (°C)

HydrogenHydrogenHydrogenNeonNeonOxygenOxygenArgonMercuryWaterWaterGalliumWater (2)IndiumTinZincAntimony (2)Aluminum SilverGoldCopper

H2H2H2NeNeO2O2ArHg

H2OH2OGa

H2OInSnZnSbAlAgAuCu

Triple pointLiquefaction point

Boiling pointTriple pointBoiling pointTriple pointBoiling pointTriple pointTriple pointFusion pointTriple pointFusion pointBoiling pointFusion point

Solidification pointSolidification pointSolidification pointSolidification pointSolidification pointSolidification pointSolidification point

13.8117.04220.282

(1)27.10254.36190.188

(1)(1)

273.15273.16

(1)373,15

(1)505.118692.73903.89

(1)1235.931337.58

(1)

-259.34-256.108-252.868

(1)-246.048-218.789-182.962

(1)(1)0

0.01(1)100(1)

231.968419.58630.74

(1)961.93

1064.43(1)

13.80317.03620.27124.556

(1)54.358

(1)83.806234.316273.15273.16302.915373.124426.749505.078692.677

(1)933.4731234.931337.331357.77

-259.347-256.114-252.879-248.594

(1)-218.792

(1)-189.344-38.834

00.01

29.76599.974

156.599231.928419.527

(1)660.323961.78

1064.181084.62



PHYSICAL QUANTITIES

120

The Most Widely Used Temperature Sensors

Standardized Types of Resistance Thermometers (table 3):• Platinum resistance thermometers: According to technical standard IEC 60751• Nickel and copper resistance thermometers: According to legal standard OIML R 84

For the characteristics of standardized resistance thermometers (or thermoresistances), also see table 4 for the tolerance classesand table 5 for the resistance values for the various types of standardized resistance thermometers.

(1) According to international technical standard IEC 60751(2) According to international legal standard OIML R 84(3) Temperature value with sign (t)(4) Coefficient C applicable only under 0° C and multiplied by the factor (t – 100°C)

(0) Or more precisely, resistance thermometer detectors (RTD)(1) According to international technical standard IEC 60751(2) According to international legal standard OIML R 84(3) Temperature module without sign t(4) Equivalent to the drop cap of the type of material followed by the acronym RT (resistance thermometer)

Table 3. Temperature Limits and Interpolating Polynomials for Normalized Resistance Thermometers

MaterialType

TemperatureLimits

(°C)

TemperatureCoefficient

(/°C)

Interpolating Polynomial (3)Rt = Ro (1 + A•t + B•t2 + C•t3)

(Ω)

Platinum (1) – 200 / +850 3.85 • 10-3 A = 3.9083 • 10 –3

B = – 5.7750 • 10 –7

C = – 4.1830 • 10 –12 (4)

Nickel (2) – 60 / +180 6.17 • 10-3 A = 5.485 • 10 –3

B = 6.650 • 10 –6

C = 2.805 • 10 –11

Copper (2) – 180 / +200 4.26 • 10-3 A = 4.260 • 10 –3

Table 4. Temperature Ranges and Tolerance Classes of Standardized Resistance Thermometers (Thermoresistances)

ThermoresistanceType(0)

Commercial Denomination (4)

ToleranceClasses

TemperatureRanges

(°C)

ToleranceValues

(°C)

Platinum – Pt (1) PRT AAABC

– 50 / + 250– 100 / + 450– 200 / + 600– 200 / + 600

± (0.10°C + 1.7•10-3t) (3)± (0.15°C + 2.0•10-3t) (3)± (0.30°C + 5.0•10-3t) (3)± (0.60°C + 10.0•10-3t) (3)

Nickel – Ni (2) NRT CC

0 / + 180– 60 / 0

± (0.20°C + 8.0•10-3t) (3)± (0.20°C + 16.5•10-3t) (3)

Copper – Cu (2) CRT BC

–50 / + 200–50 / + 200

± (0.25°C + 3.5•10-3t) (3)± (0.50°C + 6.5•10-3t) (3)

Table 5. Resistance Values of the Standardized Resistance Thermometers with 100 Ω @ 0°C:Values Ω versus °C in the range –200 to 600°C

Type –200 –150 –100 –50 0 50 100 150 200 250 300 350 400 450 500 600

PRT 18.52 39.72 60.26 80.31 100.00 119.40 138.51 157.33 175.86 194.10 212.05 229.72 247.09 264.18 280.98 313.71

NRT 74.21 100.00 129.17 161.72 198.68

CRT 78.70 100.00 121.30 142.60 163.90 185.20




TEMPERATURE

121

Standardized Types of Thermocouples (TC) (table 6):

• Thermocouples of metals in alloy: According to International Electrotechnical standard IEC 60584• Thermocouples of pure metals: According to International Electrotechnical standard IEC 62460

For the characteristics of standardized thermocouples see:

• Table 7 for the tolerance classes of thermocouples alloy• Table 8 for the tolerance classes of extension and compensating cables• Table 9 for the connecting cables in accordance with international standard IEC and national standards• Table 10 for the values of the electromotive force for various thermocouples standardized by IEC

(1) Thermocouples in pure metals (IEC 62460) have no identifying letter, but rather the component metals symbols(2) The Copper-Nickel alloy is commonly called Constantan

(1) Tolerance values are always worth the greater value.(2) For types A, B, C, the Tolerance Class 1 is not foreseen.

Table 6. Temperature Limits of Standardized Thermocouples (IEC 60584-1)

ThermocoupleType(1)

ThermocoupleMaterials Temperature

Range

CommercialDenomination

(2)Positive Conductor Negative Conductor

TEJKNSRBCA

Copper Nickel – ChromiumIron Nickel – ChromiumNickel – Cr – SiPlatinum – 10% RhPlatinum – 13% RhPlatinum – 30% RhTungsten – 5% ReTungsten – 5% Re

Copper – Nickel Copper – Nickel Copper – Nickel Nickel – AluminumNickel – SiliconPlatinumPlatinum Platinum – 6% RhodiumTungsten – 26% RheniumTungsten – 20% Rhenium

– 270 / 400– 270 / 1000– 210 / 1200– 270 / 1300– 270 / 1300– 50 / 1760– 50 / 1760

0 / 18200 / 23150 / 2500

Copper ConstantanChromel Constantan

Iron Constantan Chromel Alumel

Nicrosil Nisil

Table 7. Tolerance Classes of Standardized Thermocouples (IEC 60584-2)

ThermocoupleType

ThermocoupleMaterials

Tolerance Classes (1)

1 2Positive Conductor Negative Conductor

TEJKNSRBCA

Copper Nickel – ChromiumIron Nickel – ChromiumNickel – Cr – SiPlatinum – 10% RhPlatinum – 13% RhPlatinum – 30% RhTungsten – 5% ReTungsten – 5% Re

Copper – Nickel Copper – Nickel Copper – Nickel Nickel – AluminumNickel – SiliconPlatinumPlatinum Platinum – 6% RhodiumTungsten – 26% RheniumTungsten – 20% Rhenium

0.5°C or 0.4%1.5°C or 0.4%1.5°C or 0.4%1.5°C or 0.4%1.5°C or 0.4%1.0°C or 0.2%1.0°C or 0.2%

(2)(2)(2)

1.0°C or 0.75%2.5°C or 0.75%2.5°C or 0.75%2.5°C or 0.75%2.5°C or 0.75%1.5°C or 0.25%1.5°C or 0.25%1.5°C or 0.25%

1.0% > 425°C1.0% > 1000°C



PHYSICAL QUANTITIES

122

(1) The extension cable is of the same constituents as the thermocouple materials, used for common thermocouples: T, E, J, K, N.(2) The compensation cable is made of other materials than those constituting the thermocouple, used for precious thermocouples:R, S, B (for the latter, they are usually used for normal copper cables with typical maximum error of 3.5° C).

(*) For type B thermocouples, common copper cables in the range up to 100°C are usually used.(+) Conductor +(–) Conductor –(S) Outer Sheath

Table 8. Tolerance Classes of Extension (X) and Compensation (C) Cables for Thermocouples (IEC 60584-3)

CableType

Cable Symbol

Tolerance Classes Cable Temperature

Range

MeasureJunction

Temperature1 2

EXTENSION(1)

TXEXJXKXNX

± 30 μV (0.5°C)± 120μV (1.5°C)± 85μV (1.5°C)± 60μV (1.5°C)± 60μV (1.5°C)

± 60 μV(1.0°C)± 200 μV(2.5°C)± 140 μV(2.5°C)± 100 μV(2.5°C)± 100 μV(2.5°C)

– 25°C / +100°C– 25°C / +200°C– 25°C / +200°C– 25°C / +200°C– 25°C / +200°C

300°C500°C500°C900°C 900°C

COMPENSATION(2)

NCKCAKCB

RCA/SCARCB/SCB

–––––

± 100 μV(2.5°C)± 100 μV(2.5°C)± 100 μV(2.5°C)± 30 μV (2.5°C)± 60 μV (5.0°C)

0°C / +150°C0°C / +150°C0°C / +100°C0°C / +100°C0°C / +200°C

900°C900°C900°C1000°C1000°C

Table 9. Matching the Colors of Thermocouple Wires between IEC 60584-3 and Other National Standards

Cable forThermocouple

Type

Colors of Sheath and Cables According to:

(INTERNAT.)IEC

(U.S.)ANSI

(U.K.)BS

(D)DIN

(F)NFE

(J)JIS

T

(S) Brown Brown Blue Brown Blue Brown

(+) Brown Blue White Red Yellow Red

(–) White Red Blue Brown Blue White

E

(S) Violet Brown Brown Black Violet Violet

(+) Violet Violet Brown Red Yellow Red

(–) White Red Blue Black Violet White

J

(S) Black Brown Black Blue Black Yellow

(+) Black White Yellow Red Yellow Red

(–) White Red Blue Blue Black White

K

(S) Green Brown Red Green Yellow Blue

(+) Green Yellow Brown Red Yellow Red

(–) White Red Blue Green Violet White

N

(S) Pink Brown Orange

(+) Pink Orange Orange

(–) White Red Blue

R/S

(S) Orange Green Green White Green Black

(+) Orange Black White Red Yellow Red

(–) White Red Blue White Green White

B (*)

(S) Grey Grey Grey Grey

(+) Grey Grey Red Red

(–) White Red Grey White



TEMPERATURE

123

Values in mV versus °C, in the range –200 to 1200°C, with thermocouple reference junction @ 0°C

Table 10. Values of the Various Types of Normalized Thermocouples Consisting of Alloy Metals (IEC 60584) and Pure Metals (Au-Pt and Pt-Pd: IEC 62460)

Type – 200 – 100 0 100 200 300 400 500 600 700 800 900 1000 1100 1200

T –5.603 –3.379 0 4.279 9.288 14.862 20.872

E –8.825 –5.237 0 6.319 13.421 21.036 28.946 37.005 45.093 53.112 61.017 68.787 76.373

J –7.890 –4.633 0 5.269 10.779 16.327 21.848 27.393 33.102 39.132 45.494 51.877 57.953 63.792 69.553

K –5.891 –3.554 0 4.096 8.138 12.209 16.397 20.644 24.905 29.129 33.275 37.326 41.276 45.119 48.838

N –3.990 –2.407 0 2.774 5.913 9.341 12.974 16.748 20.613 24.527 28.455 32.371 36.256 40.087 43.846

S 0 0.646 1.441 2.323 3.259 4.233 5.239 6.275 7.345 8.449 9.587 10.757 11.951

R 0 0.647 1.469 2.401 3.408 4.471 5.583 6.743 7.950 9.205 10.506 11.850 13.228

B 0 0.033 0.168 0.431 0.787 1.242 1.792 2.431 3.154 3.957 4.834 5.780 6.786

C 0 1.451 3.090 4.865 6.732 8.657 10.609 12.559 14.494 16.398 18.260 20.071 21.825

A 0 1.336 2.871 4.512 6.203 7.908 9.605 11.283 12.933 14.549 16.127 17.662 19.150

Au-Pt 0 0.778 1.845 3.142 4.633 6.301 8.135 10.132 12.291 14.609 17.085

Pt-Pd 0 0.569 1.208 1.933 2.781 3.787 4.974 6.352 7.917 9.657 11.557 13.601 15.772



PHYSICAL QUANTITIES

124

Standardized Types of Thermometers to Radiation (also called pyrometers):

• Pyrometers operating in the red radiation: OIML R18• Pyrometers operating in the red and infrared radiation: IEC 62492

For the measuring characteristics of pyrometers and relative sensors, see respectively:

• Table 11 for the accuracy classes depending on the measurement temperature• Table 12 for the applicable sensors in relation to the measuring range to be detected

For the operating characteristics of pyrometers related to the emissivity of the bodies to be measured and the transmissivity of theinterposed media, see respectively:

• Table 13 for the emissivity (ε) of the bodies to be measured (for black body coinciding with 1)• Table 14 for the transmissivity (τ) of the interposed medium (for pure air N2+O2 coinciding with 1)

(1) Maximum permissible errors in % of the upper limit of the temperature measurement range of the pyrometer(2) Mean deviation values tolerated for five measures between the indicated temperature and the reference(3) Maximum repeatability values tolerated in five measures to the same reference temperature

Table 11. Standardization of Monochromatic Pyrometers Operating @ 0.65 µm (OIML R 18)

AccuracyClass

TemperatureRange

(°C)

Maximum Permissible Errors (1)

Deviation (2)(%)

Repeatability (3)(%)

Normal 400 – 800 800 – 14001400 – 20002000 – 32003200 – 6000

± 1.5± 1.5± 1.5± 2.5± 4.0

11123

Special 400 – 800800 – 1400

1400 – 20002000 – 32003200 – 6000

± 1.0± 0.6± 0.6± 1.2± 2.0

0.500.250.250.501.00

Table 12. Measuring Spectral Bands of Infrared Pyrometers with Various Sensors

SensorSpectral Band

(μm)

Minimum Temperature Measurable

(°C) (K)

Human eye 0.38 – 0.76 > 600 > ≈ 900

Si 0.5 – 1.0 > 400 > ≈ 700

PbS 1 – 3 > 200 > ≈ 500

PbSe 2 – 4 > 100 > ≈ 400

InAs 2 – 4 > 100 > ≈ 400

InSb 2 – 5 > 0 > ≈ 300

HgCdTe 5 – 15 < 0 < ≈ 300

Pyroelectric 0.5 – 20 < 0 < ≈ 300

Thermoelectric 0.5 – 20 < 0 < ≈ 300



TEMPERATURE

125

* In these applications, the coefficient of transmissivity is much less than 1, and therefore are bands to avoid.

Calibration and Metrological Confirmation Procedures1.4.1 Glass thermometers : TG : ASTM E 771.4.2 Dial thermometers (and digital) : TD : EN 13190 1.4.3 Thermoresistances : TR : IEC 607511.4.4 Thermocouples : TC : IEC 605841.4.5 Temperature transmitters : TT : IEC 607701.4.6 Temperature calibrators : TU : EURAMET 111.4.7 Calibration furnaces : TF : EURAMET 13 1.4.8 Radiation thermometers : TP : OIML R 18 & IEC 62942

For Other Temperature Meters• Clinical thermometers : OIML R 7 from 35 to 42°C (with MTE +0.1/–0.15°C)• Thermometers for refrigeration : EN 13485 according to EC Directive 92/1 (with MTE ≤ 0.5°C)• Thermometers for sterilization : EN 285 according to EC Directive 93/42 (with MTE ≤ 0.3°C)

The latter thermometers can follow the procedure for dial thermometers, EN 13190 (1.4.2) with at least three calibration pointsdistributed over the measurement range; however, they should follow the specific method described in the relevant technicalnormative references and legal regulations.

Table 13. Typical Emissivity Coefficient ε @ 0.65 μm for Various Materials

Material Type Material State Emissivity Coefficient

Aluminum 0.30

Beryllium 0.61

Carbon 0.80 – 0.95

ChromeNot oxidized 0.35

Oxidized 0.87

CobaltNot oxidized 0.36

Oxidized 0.77

Copper 0.10

Gold 0.14

IronNot oxidized 0.36

Oxidized 0.80 – 0.95

Molybdenum 0.40

NickelNot oxidized 0.36

Oxidized 0.85 – 0.95

Palladium 0.33

Rhodium 0.26

Silver 0.07

SteelNot oxidized 0.35

Oxidized 0.85

Tantalum 0.50

VanadiumNot oxidized 0.35

Oxidized 0.70

Zirconium 0.32

Table 14. Spectral Bands of Atmospheric Absorption in the Infrared (*)

Substance Spectral Band Absorption (μm)

Carbon dioxide 1.3–1.5 – 1.8–2.0 – 2.4–3.2 – 4.2–4.4 – 14–20

Water vapor 0.95–1.05 – 1.1–1.2 – 1.3–1.5 – 1.8–2.0 – 5.0–8.0




INTRODUCTION

191

2. Chemicals for Liquids

This second section describes the requirements and specific criteria for the management and calibration of measuring instrumentsof chemical quantities for liquids, that is, for:

2.1 pH2.2 Redox2.3 Turbidity2.4 Conductivity2.5 Dissolved Oxygen2.6 Dissolved Ions2.7 Colorimetry2.8 Refractometry

For each quantity, the handbook will succinctly present its SI units, any specific definitions, the main operating principles, and anyreference tables. In addition to the main types of instruments, it will present the relative operating procedure of calibration andmetrological confirmation articulated on the following points:

1. Scope and Purpose2. Identification and Classification3. Normative References4. Ambient Conditions5. Initial Checks6. Calibration Method7. Calibration Verification8. Calibration Results9. Metrological Confirmation



PH

193

2.1 pH


The pH is the evaluation of hydrogen and its relationship with the concentration or the activity of H+ ions in the liquid. The pH valueis the negative logarithm of the concentration (or activity) of “hydrogen ions” (H+ or H3O+). It generally ranges from 0 for the acids to14 for the bases (7 is neutral for pure water).

Typically, the pH is detected through a chain of measuring and reference electrodes (of the type with two separate electrodes, or twoelectrodes inserted into a combined measurement device, otherwise called mono tubular) that uses the Nernst law:

E = Eo + (RT/nF) • ln “concentration” H+

whereE = measurement potential (function of concentration H+)Eo = zero potential (function of asymmetry of the measuring electrodes of the pH)R = gas constant (8.3144 J/K•mol)F = Faraday constant (96493 C/mol)T = temperature in kelvin (typically 25°C)n = number of ions (1 per H+)ln = natural logarithm (concentration H+)

The Nernst slope is 59.159 mV/pH at 25°C. It is given in table 1 for other temperatures, according to IEC 60746-2.

Table 2 shows by example the typical pH of some common substances of general interest and application.

Table 1. Nernst Slope with Varying Temperature

Temperature Nernst Slope (mV/pH)

0 54.1995 55.19110 56.18315 57.17520 58.16725 59.15930 60.15235 61.14440 62.13645 63.12850 64.120

Table 2. Typical pH Values of Some Substances

Substance pH

Strong acids < 1.0Gastric acid 2.0 Lemon juice 2.4 Cola 2.5 Vinegar 2.9 Orange juice 3.5 Beer 4.5 Coffee 5.0 Tea 5.5 Acid rain 6.0 Milk 6.5 Pure water 7.0 Human spittle 6.5–7.4 Blood 7.35–7.45 Sea water 8.0 Laundry soap 9.0–10.0 Ammonia 11.5 Chlorine bleach 12.5 Caustic soda 13.5



CHEMICAL FOR LIQUIDS

194

Calibration Buffer Solutions Normalized

The planned buffer solutions for calibration and periodic testing of pH meters are standardized by reference to IEC 60746-2, or bytable 3 for the compositions of the buffer solutions and table 4 for the values of buffer solutions at different temperature.

Table 3. Compositions of the Reference Buffer Solutions (IEC 60746-2)

Buffer Solution Substance Molecular formulaMolarity

mol • kg–1Mass

g • dm–3

A Potassium tetraoxalate KH3C4O6 • 2H2O 0.1 25.101

B Potassium hydrogen tartrate

KHC4H4O6 Saturated at 25°C 6.4

C Potassium hydrogren phthalate

KHC8H4O4 0.05 10.12

D Disodium hydrogen phosphate&Potassium dihydrogen phosphate

Na2HPO4

KH2PO4

0.025

0.00869

3.533

3.388

E Disodium hydrogen phosphate&Potassium dihdrogen phosphate

Na2HPO4

KH2PO4

0.03043

0.025

4.302

1.179

F Tris*&Tris hydrocholoride

(CH2OH)3CNH2

(CH2OH)3CNH2•HCI

0.01667

0.05

1.999

7.800

G Disodium tetraborate Na2B4O7•10H2O 0.05 19.012

H Disodium tetraborate Na2B4O7•10H2O 0.01 3.806

I Sodium hydrogen carbonate&Sodium carbonate

NaHCO3

Na2CO3

0.025

0.025

2.092

2.640

J Calcium hydroxide Ca(OH)2 Saturated at 25°C 1.5

*Tris (hydroxymethyl) aminomethaneNote: All reagents shall be of analytical grade and the conductivity of the water shall be no greater than 2pS cm–1 (at 25°C).



PH

195

Most Used Normalized Calibration Buffer Solutions

In general, the most used buffer solutions for the calibration and periodic testing of pH meters are reported in table 5, derived fromearlier tables 3 and 4, in accordance with the reference standard IEC 60746-2.

Selection of Glass Measuring Electrodes

Figure 1 illustrates the recommended use of glass electrodes for pH as a function of temperature:G – General for each pH and low temperatures E – Particular for low pH and high temperatureS – Standard for low pH and low temperatures L – Special for high pH and high temperature


2.1.1 pH meters analog and digital: AP: IEC 60746-2

Table 4. Values of the Buffer Solutions (IEC 60746-2)

TamponeBuffer

0°C 5°C 10°C 15°C 20°C 25°C 30°C 35°C 37°C 40°C 50°C 60°C 70°C 80°C 90°C 95°C

A(2) 1.67 1.67 1.67 1.67 1.68 1.68 1.68 1.68 1.69 1.69 1.71 1.72 1.74 1.77 1.75 1.81

B(1) — — — — — 3.557 3.552 3.549 3.548 3.547 3.549 3.55 3.57 3.60 3.63 3.65

C(1) 4.000 3.998 3.997 3.998 4.000 4.005 4.011 4.018 4.022 4.027 4.050 4.06 4.12 4.16 4.21 4.24

D(1) 6.984 6.951 6.923 6.900 6.881 6.865 6.853 6.844 6.841 6.838 6.833 6.84 6.85 6.86 6.88 6.89

E(1) 7.534 7.500 7.472 7.448 7.429 7.413 7.400 7.389 7.386 7.380 7.367 — — — — —

F(2) 8.47 8.30 8.14 7.99 7.84 7.70 7.56 7.43 7.38 7.31 7.07 — — — — —

G(2) 9.51 9.43 9.36 9.30 9.25 9.19 9.15 — 9.09 9.07 9.01 8.93 8.90 8.88 8.84 8.89

H(1) 9.464 9.395 9.332 9.276 9.225 9.180 9.139 9.102 9.088 9.068 9.011 8.97 8.93 8.91 8.90 8.89

I(1) 10.317 10.245 10.179 10.118 10.062 10.012 9.966 9.926 9.910 9.889 9.828 9.75 9.73 9.73 9.75 9.77

J(2) 13.42 13.21 13.00 12.81 12.63 12.45 12.29 12.13 12.07 11.98 11.71 11.45 — — — —

Table 5. Main Buffer Solutions Used for Calibration Verification of pH Meters (IEC 60746-2)

Temperature(°C)

pH Buffers Main Used in Temperature

CKHC8H4O4

DKH2PO4

INaH2CO3

JCa(OH)2

10 3.997 6.923 10.179 13.0015 3.998 6.900 10.118 12.8120 4.000 6.881 10.062 12.6325 4.005 6.865 10.012 12.4530 4.011 6.853 9.966 12.29

Figure 1. Typical Uses of Glass Measurement Electrodes in Relation to pH and to the Measuring Temperature

1 3 5 7 9 11 13 [pH]

[°C]

125

100

75

50

25

0

S

E L

G



CHEMICAL FOR LIQUIDS

196

2.1.1. pH Meters Analog and Digital

1. Scope and PurposeThis procedure applies to analog and digital pH meters, to a measuring electrode and a separate reference, or to those integrated inthe same electrode, otherwise called mono tubular.

2. Identification and ClassificationBefore information about the new instrument is used in the application, it must be filed in accordance with the instrument card at theright, defining the procedures, the normative references, and the required checks and results. The instrument must then beconfirmed metrologically for the application, including the instrument’s recalibration, if necessary.

3. Normative References• IEC 60746-1 (2003) : Expression of performance of electrochemical analyzers: General• IEC 60746-2 (2003) : Expression of performance of electrochemical analyzers: pH value• OIML R 54 (1981) : pH scale for aqueous solutions


5. Initial ChecksBefore starting any operation, check that the instrument does not indicate traces of rupture, wear, or alteration of parts, such aselectrode cleaning, unfilled electrolyte solutions, or indicators. Install and connect the instrument in the measurement system, andmake sure that there is proper ionic contact between the measurement electrodes and the calibration reference measurementsolution.

6. Calibration MethodWhen performing calibration, compare with a reference standard:

• With standard reference solutions in a special dedicated support (figure A)• With standard reference solutions automatically slaved (preferable) (figure B)• With mV generator instruments, only suitable for verification of the indicators of pH meters (figure C)

In any case, it has a lower measurement uncertainty, possibly one-third of that of the instrument in calibration.

7. Calibration VerificationThe verification should be performed on at least three points, distributed with respect to the measuring standard value (STD):

3 pH; STD + 3 pHFor example, for applications at neutral pH: 4 pH; 7 pH; 10 pH, or only on two calibration points, if it generally works with just acidicor basic solutions. At each pH value, wait a few minutes before taking the measurement values of the calibration instrument.

8. Calibration ResultsCalibration results should be reported on the instrument card to first be processed and then valued against the Maximum ToleratedError (MTE) or Maximum Tolerated Uncertainty (MTU):


If the check is not positive, it will be necessary to recalibrate the instrument, repeat the calibration verification (point 7), or downgradeor alienate the instrument.


• The result of the metrological confirmation (positive, negative: declassification or alienation)• The signature of those who made the verification and the next verification date





PH

197


pH Meters(analog and digital)

Card Number XX-AP

IDENTIFICATION AND METROLOGICAL DATA

Instrument identification AP11 Measuring range 0–14 pH

Instrument classification Process Calibration range 4–10 pH

Instrument denomination pH meter Accuracy class 0.2 pH

Manufacturer ABC Measure resolution (Eres) 0.1 pH

Model AP2 Max Tolerated Error (MTE) 0.2 pH

Serial number XYZ Max Tolerated Uncertainty (MTU) 0.3 pH

Date of acquisition 01.02.2010 Reference standard uncertainty (Uref) 0.1 pH

Location of installation Process AP 11 Certificate number of standard 1111

Installation conditions Vertical Fluid exercise/calibration Water/std. solution

Utilization conditions Specify Fluid filling/reference Specify

APPLICABLE PROCEDURES AND NORMATIVES

Calibration procedure PP-AP Maintenance procedure Manufacturer spec.

Confirmation procedure PP-AP Normative reference IEC 60746-2

REQUIRED CONTROLS

Calibration YES NO

Confirmation YES NO

Certification YES NO

Body Control Internal External

TRACEABILITY OF MEASUREMENT

Calibration and ConfirmationInternal traceability to reference standard AS 11


INTERVAL OF METROLOGICAL CONFIRMATION

3 months 6 months 1 year 2 years

RESULTS OF CONFIRMATION

Date of Control

Body Control

Number ofReport


DriftMRE/pH

Signature Vision

Deadline Notes

01.06.2017 Internal XX-AP Positive 0.1 White 01.06.2018

RESULTS OF LAST CONFIRMATION

Was the adjustment made before the verification? YES NOSolution

ReferenceTable 5

(pH)

RELIEVED VALUES RELIEVED ERRORS Max Relieved ErrorEmax(pH)

Indication Elaboration

(pH) (pH)

4.0 ≡ Solution C 4.1 0.1

6.9 ≡ Solution D 7.0 0.1

10.0 ≡ Solution I 10.0 0.0 0.1

RESULTS OF METROLOGICAL CONFIRMATION

MRE < MTE 0.1 pH < 0.2 pH YES NO

OR ALTERNATIVELY

MRU < MTU YES NO

THE NEXT VERIFICATION MUST BE CARRIED OUT WITHIN 01.06.2018

MetrologicalFunction


2 22 2 2 2max 0.1 0.1 0.12 2 0.16 0.302 2 1.73 3.463 2. 3

Uref E EresMRU pH pH

= ⋅ + + = ⋅ + + = <



TERMS

345

2. Terms Index for the Management of Measuring Instruments

TERM SYMBOL PAGE

Accuracy 31

Accuracy class Cl 31

Assessment of conformity (CE) 61

Audit Trail 65

Bureau International de Poids et Mesures BIMP 9

Calibration certificate 34

Calibration report 34

Calibration report (As Found) 34

Calibration report (As Left) 34

Characteristic, metrological 42

Characteristic, metrological for measuring equipment MEMC 52

Characteristic, metrological for reference equipment REMC 52

Code of Federal Regulation CFR 65

Comité Internationale des Poids et Mesures CIPM 9

Compatibility of Measures 22

Conference Générale des Poids et Mesures CGPM 9

Conformity assessment modules (CE) 61

Conformity marking (CE) 61

Control chart 46

Coverage factor 28

Customer Metrological Requirement CMR 42

Distribution, normal (or Gaussian) 25

Distribution, rectangular 25

Distribution, triangular 25

Environmental Management System EMS 35

Error E 32

Error, eccentricity Eecc 26

Error, indication (maximum) Emax 26

Error, interpolation Eint 27

Error, parallelism Epar 26

Error, planarity Epla 26

Error, repeatability Erep 27

Error, resolution Eres 26

Essential Safety Requirements ESR 59

European cooperation for Accreditation EA 17

Evidence of conformity instruments 57

Food and Drug Administration FDA 65

Good Automated Manufacturing Practices GAMP 66

Good Practice Guidelines GPG 66

Good Practices GxP 66

International Accreditation Forum IAF 15



ANALYTICAL INDEX

346

International Laboratory Accreditation Cooperation ILAC 15

International Organization for Accreditation Bodies 15

International System of units SI 9

Italian Body Accreditation ACCREDIA 18

Key Performance Indicators KPI 68

Labels of evidence of conformity instruments 58

Maximum Admitted Error MAE 56

Maximum Permissible Error MPE 63

Maximum Relieved Error MRE 54

Maximum Relieved Uncertainty MRU 55

Maximum Tolerated Error MTE 54

Maximum Tolerated Uncertainty MTU 55

Measurand 31

Measurement 31

Measurement accuracy 31

Measurement equipment selection 50

Measurement Management System MMS 39

Measurement method, direct 31

Measurement method, indirect 31

Measurement process control 42

Measurement traceability 35

Measuring equipment (or measuring instrument) 42

Measuring instrument 31

Measuring instrument (calibration and verification procedures) 33

Measuring instrument (calibration conditions) 29

Measuring instrument (criteria for instrument selection) 49

Measuring Instruments Directive MID 59

Metre convention 10

Metrological confirmation 42

Metrological confirmation intervals (definitions) 43

Metrological confirmation intervals (examples) 47

Metrological confirmation intervals (review) 45

Metrological function 42

Metrological traceability 31

Metrological traceability chain 31

National Accreditation Bodies NAB 17

National Metrological Institutes NMI 20

Procedure, adjustment 34

Procedure, calibration 34

Procedure, maintenance 34

Procedure, measurement 34

Procedure, operational 34

Procedure, verification 34

Product Reference Value (process or service) PRV 52

Product Tolerance Amplitude (process or service) PTA 52



TERMS

347

Product Tolerance Band (process or service) PTB 52

Quality Management System QMS 35

Reference equipment selection 50

Reference material 31

Reference measurement standard 31

Standard deviation s 27

Standard deviation, equivalent σeq 27

Standard Operation Procedure SOP 66

Standard, primary measurement 31

Standard, reference measurement 31

Standard, secondary measurement 31

Standard, traveling measurement 31

Test Uncertainty Ratio TUR 50

Traceability of measures 21

Type examination (CE) 60

Uncertainty 23

Uncertainty, combined uc 23

Uncertainty, expanded U 23

Uncertainty, type u 23

Uncertainty, type A 23

Uncertainty, type B 23

Verification of conformity of measuring instrument (application methods) 53

Verification of conformity of measuring instrument (process or service) 53

Verification, first (CE) 64

Verification, periodic (CE) 64

Zone, ambiguity 56

Zone, conformity 56

Zone, nonconformity 55

Zone, secure conformity ZSC 56

Zone, secure nonconformity 56

Zone, tolerance (specified) 56



INSTRUMENTS INDEX

349

3. Instruments Index for the Calibration of Measuring Instruments

INSTRUMENT MEASURE PAGE

Accelerometers Vibration 302

Aerometers by immersion Density 174

Ammeters (see indicators) Electrical quantities 318

Amperometrics (or polarimetrics) Dissolved oxygen 220

Analyzers, amperometric cell Dissolved oxygen 219

Analyzers, catalytic combustion (for gas) Combustible gases 256

Analyzers, electrochemical (for gas) Comburent gases 251

Analyzers, flame ionization (for gas) Combustible gases 255

Analyzers, fluorimetric cell (for oxygen) Dissolved oxygen 219

Analyzers, infrared (IR) Infrared gases 244

Analyzers, paramagnetic (for gas) Comburent gases 251

Analyzers, thermal conductivity (for gas) Combustible gases 256

Analyzers, ultraviolet (UV) Ultraviolet gases 248

Aphrometers (see manometers) Pressure 78

Balance, mass Mass 188

Balance, pressure Pressure 84

Barometers (see manometers) Pressure 78

Calibrators, acoustic Sound and noise 311

Calibrators, humidity (saturated salt solutions) Humidity 146

Calibrators, pressure Pressure 82

Calibrators, temperature Temperature 136

Calipers (analog and digital) Length 284

Chromatographs Gas chromatography 264

Colorimeters Colorimetry 232

Colorimetry Colorimetry 229

Comparators Length 280

Conductivity meters Conductivity 214

Current clamps Electrical quantities 334

Densimeters, immersion (or aerometers) Density 174

Densimeters, pressure Density 170

Densimeters, vibration (or rotation) Density 172

Dew Point (DP) Humidity 148

Dissolved ions Dissolved ions 223

Dissolved oxygen Dissolved oxygen 217

Dynamometers Force 288

Energy meters Electrical quantities 330

Flame Ionization Detector (FID) Gas chromatography 262

Flame Photometric Detector (FPD) Gas chromatography 262

Flowmeters (or measurers of flow) Flow 87

Fluorimeters (or luminescence) Dissolved oxygen 220

Frequency meters (see indicators) Electrical quantities 318




ANALYTICAL INDEX

350

Frost Point (FP) Humidity 148

Gas chromatographs Gas chromatography 264

Gas chromatography Gas chromatography 261

Gas spectrometers Gaspectrometry 270

Gas spectrometry Gaspectrometry 267

Gauge blocks Length 278

Hydrometers (by immersion) Density 174

Hydrostatics (at pressure) Level 114

Hygrometers, absolute humidity Humidity 148

Hygrometers, relative humidity Humidity 150

Indicators (analog and digital) Electrical quantities 318

Ion Selective Electrodes (ISE) Dissolved ions 223

Level meters (or measurers of level) Level 113

Load cells (or dynamometers) Force 288

Lower Explosive Limit (LEL) Combustible gases 257

Magnetics (or electromagnetics) Flow 98

Manometers, analog (or dial) Pressure 78

Manometers, digital (or numeral) Pressure 82

Manometers, electromechanical Pressure 82

Manometers for blood pressure (sphygmomanometers) Pressure 77

Manometers for extinguishers Pressure 77

Manometers for medical Pressure 77

Manometers for tires Pressure 77

Manometers for welding Pressure 77

Manovacuumeters (see manometers) Pressure 78

Mass (standards) Mass 179

Massics (Coriolis) Flow 108

Measurers for comburent gases Comburent gases 251

Measurers for combustible gases Combustible gases 255

Measurers of chromatography Gas chromatography 261

Measurers of colorimetry Colorimetry 232

Measurers of conductivity (or electrical conductibility) Conductivity 211

Measurers of couple (or torque wrenches) Couple 291

Measurers of density (or volumic mass) Density 163

Measurers of dissolved ions Dissolved ions 226

Measurers of dissolved oxygen Dissolved oxygen 220

Measurers of electrical quantities Electrical quantities 315

Measurers of flow (or flowmeters) Flow 87

Measurers of force Force 287

Measurers of humidity Humidity 143

Measurers of infrareds Infrared gases 243

Measurers of length Length 275

Measurers of level Level 113

Measurers of mass Mass 175

Measurers of pH pH 193



INSTRUMENTS INDEX

351

Measurers of pressure Pressure 75

Measurers of refractometry Refractometry 238

Measurers of rH rH 199

Measurers of sound and noise Sound and noise 305

Measurers of spectrometry Gaspectrometry 267

Measurers of speed (or rotation) Velocity 295

Measurers of temperature Temperature 119

Measurers of turbidity Turbidity 205

Measurers of ultraviolets Ultraviolet gases 247

Measurers of vibration (or acceleration) Vibration 299

Measurers of viscosity Viscosity 153

Measurers per combustible gases Combustible gases 258

Micrometers Length 282

Mostimeters at immersion Density 174

Multimeters (analog and digital) Electrical quantities 338

Normal Hydrogen Electrode (NHE) rH or pH 200

Nozzle (see orifice plates) Flow 92

Ohmmeters (see indicators) Electrical quantities 318

Orifice plates Flow 92

Oscilloscopes Electrical quantities 321

Oxidation Reduction Potential (ORP) rH 199

Ph meters pH 196

Phonometers Sound and noise 312

Pistonphons Sound and noise 311

Polarimetrics (or amperometrics) Dissolved oxygen 220

Psychrometers Humidity 146

Pycnometers (to weigh) Density 174

Pyrometers Temperature 140

Radar (at reflection) Level 116

Refractometers Refractometry 238

Refractometry Refractometry 235

Rh meters rH 200

Root Mean Square (RMS) Vibration 300

Saccarimeters (at immersion) Density 174

Servoaccelerometers (see accelerometers) Vibration 302

Sonar (at reflection) Level 116

Sonics (or ultrasonics) Flow 106

Sound Exposure Level (SEL) Sound and noise 309

Sound Pressure Level (SPL) Sound and noise 309

Spectrometers Gaspectrometry 270

Sphygmomanometers (see manometers for blood pressure) Pressure 77

Standard masses Mass 186

Tachometers (or velocimeters) Velocity 296

Temperature furnaces Temperature 138

Thermal (flowmeters) Flow 110



ANALYTICAL INDEX

352

Thermal Conductivity Detector (TCD) Gas chromatography 262

Thermocouples Temperature 132

Thermometers, dial or digital Temperature 128

Thermometers, glass Temperature 126

Thermometers, medical use Temperature 125

Thermometers, pyrometers Temperature 140

Thermometers, refrigeration Temperature 125

Thermometers, sterilization Temperature 125

Thermoresistances Temperature 130

Torque meters Couple 292

Torque wrenches Couple 292

Transducers, pressure Pressure 80

Transformers, measure Electrical quantities 326

Transmitters, pressure Pressure 80

Transmitters, temperature Temperature 134

Turbidimeters Turbidity 208

Turbines Flow 102

Upper Explosive Limit (UEL) Combustible gases 257

Vacuum gauges (see manometers) Pressure 78

Vacuum meters (see manometers) Pressure 78

Velocimeters (see velocity) Velocity 295

Venturi meters (see orifice plates) Flow 92

Vibrometers (see accelerometers) Vibration 302

Viscometers, differential pressure Viscosity 158

Viscometers, vibration (or rotation) Viscosity 160

Voltmeters (see indicators) Electrical quantities 318

Volumetrics Flow 104

Vortex Flow 100

Wattmeters (see indicators) Electrical quantities 318

Weight sets Mass 186




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